372 



BELL SYSTEM TECHNICAL JOURNAL 



}/i mile, the number of transpositions for J carrier operation has been 

 increased so that for the J-3 design, which was used for the new wires 

 on the Fourth Transcontinental line, there are four transpositions in 

 each eight-span interval and every pole is a potential transposition 

 point. 



VOICE FREQUENCY PHANTOMED CIRCUITS 

 OAiD (E SECTION) 



1-2 

 3-4 



)C 



1-2 

 3-4 



C CARRIER PHANTOMED CIRCUITS 

 (ALTERNATE ARM SYSTEM) 



X )E X 



X X 



)C 



1-2 

 3-4 



C CARRIER NON-PHANTOMED CIRCUITS 

 {K-8 SYSTEM) 



X W X X i\ X — 



XXX X X X )[ X X X XXX 



I -2 

 7-8* 



J CARRIER NON-PHANTOMED CIRCUITS 

 {K-8-2 system) 



X k X )f X )£ X — 



XXXXXXX3tXAX)[XXX 



I -2 

 3-4 



(j-3 system) 



-X-Hf-^<- 



X )t X 



X )[ X 



XXX x;ix X X xux x x x)tx x x x 



32 POLE SPANS OR 0.8 Ml. 



X 



X = SIDE OR PHYSICAL CIRCUIT TRANSPOSITION 

 = PHANTOM TRANSPOSITION 



• PAIR 7-8 IS SHOWN SINCE PAIR 3-4 IS NOT 

 INTENDED FOR J-SYSTEM OPERATION ON A 

 K-8-2 LINE. 



* * FOR THE VOICE FREQUENCY AND ALTERNATE ARM 

 LAYOUTS THIS DISTANCE IS 40 SPANS. 



Fig. 6 — Illustrative transposition arrangements. 



It may be seen from Fig. 6, however, that the number of transposi- 

 tions required in pairs for J carrier operation is not necessarily larger 

 than the number employed in systems intended for C carrier operation 

 with a top frequency of 30 kilocycles. The superiority of the J system 

 transposition arrangements as compared with those designed for C 

 system operation results from the choice of specific arrangements which 

 best limit the systematic effects for frequencies in the J system range. 



